A broadband microwave photonic phase noise measurement device and method

Abstract

The application discloses a broadband microwave photon phase noise measuring device and method, which comprises a laser, an electro-optic intensity modulator, a plurality of optical fiber couplers, a single-mode optical fiber, a tunable laser, a first tunable optical fiber delay line, a second tunable optical fiber delay line, a first photoelectric detector, a second photoelectric detector, a first filter, a second filter, a first amplifier, a second amplifier, a double balanced mixer, a low pass filter and a signal analyzer. The high-frequency microwave signal to be measured is down-converted into a low-frequency electric signal by using an optical heterodyne technique, and filtering is realized in the electric domain, so that the limitation of devices such as an electric mixer, an electric filter, an electric amplifier and an optical filter on the measurement frequency of the system is avoided, and the working bandwidth of the phase noise measuring system is expanded; by matching the delay of the first branch and the second branch, the influence of the local light source noise on the noise floor of the phase noise measuring system is suppressed, so that the phase noise measuring sensitivity of the system is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave source phase noise measurement and microwave photonics, and particularly relates to a wideband microwave photonics phase noise measurement device and method. BACKGROUND

[0002] With the development of microwave oscillator technology, especially the appearance of optoelectronic oscillator which can directly generate ultra-high frequency and ultra-low phase noise microwave signal[D. Eliyahu et al., "Phase noise of a high performance OEO and an ultralow noise floor cross-correlation microwave photonic homodyne system," IEEE Symposium on Frequency Control Proceedings, 811-814 (2008).], the existing phase noise measurement technology has been greatly challenged. The frequency discrimination method based on optical delay line is the most widely used measurement method at present. This method can achieve high phase noise measurement sensitivity with the help of long delay provided by low-loss optical fiber. However, in this scheme, the working bandwidth is usually limited by electronic devices such as electrical phase shifter, electrical amplifier and electrical mixer, and before electrical mixing, an electrical amplifier is usually needed to ensure that the power level of the signal meets the measurement requirements, which essentially reduces the measurement sensitivity of the system.

[0003] To solve these problems, researchers have proposed a series of photon-assisted phase noise measurement systems, which realize the functions of phase shifting and mixing in the optical domain. For example, in [D. J. Zhu et al., “Wideband phase noise measurement using a multifunctional microwave photonic processor,” IEEE Photon. Technol. Lett. 26 (24), 2434-2437 (2014).], the electrical phase shifter in the phase noise measurement system is replaced by a microwave photonic phase shifter. In [D. J. Zhu et al., “Phase noise measurement of wideband microwave sources based on a microwave photonic frequency down-converter,” Opt. Lett. 40 (7), 1326-1329 (2015).], a phase noise measurement system based on a cascaded electro-optic modulator structure is proposed, which avoids the use of an electrical mixer. However, this also brings a new problem, that is, the roll-off slope of the optical filter limits the measurement capability of low-frequency signals.

[0004] Therefore, in order to solve the limitations of electrical mixers, electrical phase shifters on the upper limit of the measurement bandwidth and optical filters on the lower limit of the measurement bandwidth, it is urgent to develop a phase noise measurement scheme with simple structure, high sensitivity and large working bandwidth. SUMMARY

[0005] To solve the above technical problems, the present application provides a wideband microwave photonic phase noise measurement device and method.

[0006] A wideband microwave photonic phase noise measurement device, comprising:

[0007] An optical beam generation module generates a continuous optical carrier signal modulated by a to-be-measured microwave signal of a to-be-measured microwave source and a frequency-adjustable local oscillator optical signal;

[0008] A coupling module divides the local oscillator optical signal into two signals, which enter a first branch and a second branch, respectively; and divides the modulated optical carrier signal into two signals, one of which is coupled into the first branch to obtain a first coupled signal, and the other of which is coupled into the second branch after being introduced into a long delay to obtain a second coupled signal;

[0009] The first processing module is arranged in the first branch and is used for introducing a delay in the first coupling signal to match the delay of the first branch and the second branch, so that the delay difference between the first coupling signal and the second coupling signal is controlled within 1 ns, to suppress the noise of the local light signal, and the first coupling signal after the delay is subjected to heterodyne detection, filtering and amplification in sequence;

[0010] The second processing module is arranged in the second branch and is used for introducing a phase shift in the second coupling signal to finely adjust the delay difference, so that the delay difference changes within 100 ps, so that the output signals of the first processing module and the second processing module are in quadrature, and the second coupling signal after the delay is subjected to heterodyne detection, filtering and amplification in sequence;

[0011] The analysis module mixes the output signals of the first processing module and the second processing module and filters out high-frequency components therefrom, and analyzes and calculates the filtered signals to obtain the phase noise of the to-be-measured microwave signal;

[0012] The frequency of the local light signal is close to the frequency of the continuous optical carrier signal, and the to-be-measured microwave signal with high frequency can be down-converted to a low-frequency signal after heterodyne detection by the first processing module and the second processing module. The frequency of the low-frequency signal is within the working frequency range of conventional electrical components.

[0013] Preferably, the light beam generation module comprises:

[0014] The laser is used to generate a continuous optical carrier signal.

[0015] The electro-optical intensity modulator is used to modulate the optical carrier signal generated by the laser by using the to-be-measured microwave signal of the to-be-measured microwave source.

[0016] The tunable laser is used to generate a frequency-adjustable local light signal.

[0017] Preferably, the coupling module comprises:

[0018] The first optical fiber coupler is used to divide the modulated optical carrier signal into a first optical carrier signal and a second optical carrier signal.

[0019] The single-mode optical fiber is used to introduce a long delay into the first optical carrier signal to obtain a delayed optical carrier signal.

[0020] a second optical fiber coupler for splitting the local light signal into a first local light signal and a second local light signal, the first local light signal entering the first branch, and the second local light signal entering the second branch;

[0021] a third optical fiber coupler for coupling the delayed optical carrier signal and the first local light signal to obtain a first coupled signal;

[0022] a fourth optical fiber coupler for coupling the second optical carrier signal and the second local light signal to obtain a second coupled signal.

[0023] Preferably, the first processing module comprises, in sequence:

[0024] a first adjustable optical fiber delay line for adjusting the delay of the first coupled signal, so that the signal transmitted in the first branch and the signal transmitted in the second branch have a delay difference within 1 ns, for offsetting the phase noise of the local light;

[0025] a first photodetector for receiving the first coupled signal and performing heterodyne detection;

[0026] a first filter for filtering out only the positive first-order sideband of the first optical carrier signal and the beat signal of the first local light signal;

[0027] a first amplifier for amplifying the electrical signal output by the first filter.

[0028] Preferably, the second processing module comprises, in sequence:

[0029] a second adjustable optical fiber delay line for finely adjusting the delay difference, so that it changes within 100 ps, by introducing a phase shift into the second coupled signal so that the relative phase difference between the electrical signals output by the first optical processing module and the second optical processing module is k is an integer;

[0030] a second photodetector for receiving the second coupled signal with the phase shift and performing heterodyne detection;

[0031] a second filter for filtering out only the positive first-order sideband of the second optical carrier signal and the beat signal of the second local light signal;

[0032] a second amplifier for receiving and amplifying the electrical signal output by the second filter.

[0033] Preferably, the analysis module comprises:

[0034] a double balanced mixer for receiving and mixing the electrical signals output by the first optical processing module and the second optical processing module;

[0035] a low pass filter for receiving and filtering high frequency components from the electrical signal output by the double balanced mixer;

[0036] a signal analyzer for analyzing the electrical signal output by the low pass filter to obtain the phase noise of the microwave signal under test.

[0037] Preferably, the electro-optical intensity modulator is a broadband Mach-Zehnder modulator.

[0038] Preferably, the tunable laser is a narrow linewidth high tuning precision laser.

[0039] A broadband microwave photonic phase noise measurement method, applied to a broadband microwave

[0040] A photonic phase noise measurement device, comprising the following steps:

[0041] S1: generating a continuous optical carrier signal and a frequency-tunable local oscillator optical signal, and modulating the continuous optical carrier signal with a microwave signal under test from a microwave source under test;

[0042] S2: dividing the modulated continuous optical carrier signal into a first optical carrier signal and a second optical carrier signal; using the second optical fiber coupler to divide the local oscillator optical signal into a first local oscillator optical signal and a second local oscillator optical signal, wherein the first local oscillator optical signal enters the first branch and the second local oscillator optical signal enters the second branch; and introducing a long delay into the first optical carrier signal to obtain a delayed optical carrier signal;

[0043] S3: coupling the delayed optical carrier signal and the first local oscillator optical signal to obtain a first coupled signal; and coupling the second optical carrier signal and the second local oscillator optical signal to obtain a second coupled signal;

[0044] S4: first adjusting the delay difference between the first branch and the second branch to be within 1 ns, and then finely adjusting the delay difference so that the output signals of the first processing module and the second processing module are in phase quadrature, and then performing heterodyne detection, filtering and amplification on the delayed first coupled signal and the second coupled signal, respectively;

[0045] S5: mixing the processed first coupling signal and the processed second coupling signal and filtering high frequency components in the mixed signal to obtain a to-be-detected signal;

[0046] S6: analyzing and calculating the to-be-detected signal to obtain the phase noise of the to-be-detected microwave signal.

[0047] Preferably, the filtering in step S4 is filtering out the beat signal of the positive first-order sideband of the optical carrier and the local light signal.

[0048] The above technical solution of the present application has the following advantages compared with the prior art:

[0049] 1. The wideband microwave photonic phase noise measurement device and method of the present application can effectively avoid the limitation of electronic devices such as electric mixers, electric filters and electric amplifiers on the measurement frequency of the system, expand the working bandwidth of the phase noise measurement system, and down-convert the high-frequency to-be-detected microwave signal to a low-frequency signal through the heterodyne detection of the first photodetector and the second photodetector by coupling a local light signal with a frequency close to that of the continuous optical carrier signal modulated by the to-be-detected microwave signal of the to-be-detected microwave source.

[0050] 2. The first adjustable optical fiber delay line is used to control the delay difference between the first branch and the second branch within 1 ns, and the second adjustable optical fiber delay line is used to make the output signals of the first processing module and the second processing module orthogonal in phase, thereby effectively suppressing the influence of the local light source noise on the noise floor of the phase noise measurement system and improving the phase noise measurement sensitivity.

[0051] The above description is only a summary of the technical solution of the present application, in order to more clearly understand the technical means of the present application, the content of the specification can be implemented, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following preferred embodiments are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0052] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to the specific embodiments of the present application and in combination with the accompanying drawings.

[0053] Figure 1 is a schematic diagram of a wideband microwave photonic phase noise measurement device of the present application.

[0054] The description of the drawings is as follows: 1, laser; 2, electro-optic intensity modulator; 3, microwave source to be measured; 4, tunable laser; 5, first fiber coupler; 6, single-mode optical fiber; 7, second fiber coupler; 8, third fiber coupler; 9, fourth fiber coupler; 10, first adjustable fiber delay line; 11, first photodetector; 12, first filter; 13, first amplifier; 14, second adjustable fiber delay line; 15, second photodetector; 16, second filter; 17, second amplifier; 18, double balanced mixer; 19, low pass filter; 20, signal analyzer. DETAILED DESCRIPTION

[0055] The present application will be further described below with reference to the drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it, but the embodiments are not limiting to the present application.

[0056] Referring to Figure 1 The present application provides a broadband microwave photonic phase noise measurement device, which comprises:

[0057] A light beam generation module generates a continuous optical carrier signal modulated by a microwave signal to be measured of a microwave source to be measured and a frequency-adjustable local oscillator light signal; comprising: a laser 1, an electro-optic intensity modulator 2 and a tunable laser 4; the laser 1 is used to generate a continuous optical carrier signal; the electro-optic intensity modulator 2 is used to modulate the optical carrier signal generated by the laser 1 with the microwave signal to be measured of the microwave source to be measured 3; the tunable laser 4 is used to generate a frequency-adjustable local oscillator light signal.

[0058] A coupling module divides the local oscillator light signal into two signals, which enter a first branch and a second branch respectively; divides the modulated optical carrier signal into two signals, one of which is coupled into the first branch to obtain a first coupled signal, and the other of which is coupled into the second branch after introducing a long delay to obtain a second coupled signal; comprising: a first fiber coupler 5, a single-mode optical fiber 6, a second fiber coupler 7, a third fiber coupler 8 and a fourth fiber coupler 9; the first fiber coupler 5 is used to divide the modulated optical carrier signal into a first optical carrier signal and a second optical carrier signal; the single-mode optical fiber 6 is used to introduce a long delay τ to the first optical carrier signal to obtain a delayed optical carrier signal; the second fiber coupler 7 is used to divide the local oscillator light signal into a first local oscillator light signal and a second local oscillator light signal, the first local oscillator light signal enters the first branch, and the second local oscillator light signal enters the second branch; the third fiber coupler 8 is used to couple the delayed optical carrier signal and the first local oscillator light signal to obtain a first coupled signal; the fourth fiber coupler 9 is used to couple the second optical carrier signal and the second local oscillator light signal to obtain a second coupled signal.

[0059] The first processing module is arranged in the first branch, and is used for introducing a delay in the first coupled signal to match the delays of the first branch and the second branch, so that the delay difference between the first coupled signal and the second coupled signal is controlled within 1 ns, to suppress the noise of the local light signal, and the first coupled signal after the delay is subjected to heterodyne detection, filtering and amplification in sequence; the first processing module comprises a first adjustable optical fiber delay line 10, a first photodetector 11, a first filter 12 and a first amplifier 13; the first adjustable optical fiber delay line is used to adjust the delay of the first coupled signal, so that the delay difference between the signal transmitted in the first branch and the signal transmitted in the second branch is within 1 ns, to offset the phase noise of the local light; the first photodetector 11 is used to receive the first coupled signal and perform heterodyne detection; the first filter 12 is used to filter out only the positive first-order sideband of the first optical carrier signal and the beat signal of the first local light signal; and the first amplifier 13 is used to amplify the electrical signal output by the first filter.

[0060] The second processing module is arranged in the second branch, and is used for introducing a phase shift in the second coupled signal, finely adjusting the delay difference, so that the delay difference changes within 100 ps, so that the output signals of the first processing module and the second processing module are in phase quadrature, and the second coupled signal after the delay is subjected to heterodyne detection, filtering and amplification in sequence; the second processing module comprises a second adjustable optical fiber delay line 14, a second photodetector 15, a second filter 16 and a second amplifier 17; the second adjustable optical fiber delay line 14 is used to finely adjust the delay difference between the optical signal transmitted in the first optical processing module and the optical signal transmitted in the second optical processing module, so that the delay difference changes within 100 ps, and a phase shift is introduced into the second coupled signal so that the relative phase difference between the electrical signals output by the first optical processing module and the second optical processing module is k is an integer; the second photodetector 15 is used to receive the second coupled signal with the phase shift and perform heterodyne detection; the second filter 16 is used to filter out only the positive first-order sideband of the second optical carrier signal and the beat signal of the second local light signal; and the second amplifier 17 is used to receive and amplify the electrical signal output by the second filter.

[0061] The analysis module mixes the output signals of the first processing module and the second processing module and filters high-frequency components therefrom; and analyzes and calculates the filtered signals to obtain the phase noise of the microwave signal to be measured; and comprises a double-balance frequency mixer 18, a low-pass filter 19 and a signal analyzer 20; the double-balance frequency mixer 18 is used to receive and mix the electrical signals output by the first optical processing module and the second optical processing module; the low-pass filter 19 is used to receive the electrical signals output by the double-balance frequency mixer 18 and filter high-frequency components therefrom; and the signal analyzer 20 is used to analyze and calculate the electrical signals output by the low-pass filter 19 to obtain the phase noise of the microwave signal to be measured; and the fast Fourier transform analyzer receives and analyzes the low-frequency signals filtered by the low-pass filter 19;

[0062] The frequency of the local-oscillation optical signal is close to the frequency of the continuous optical carrier signal, and the high-frequency microwave signal to be measured can be down-converted to a low-frequency signal after heterodyne detection by the first processing module and the second processing module, and the frequency of the low-frequency signal is within the working frequency range of conventional electrical components.

[0063] When the system is in operation, the optical carrier signal generated by the laser is modulated by the microwave signal to be measured from the microwave source to be measured, and the modulated optical carrier signal is divided into a first optical carrier signal and a second optical carrier signal after passing through the first optical fiber coupler. Meanwhile, the frequency-adjustable local-oscillation optical signal generated by the tunable laser is divided into a first local-oscillation optical signal and a second local-oscillation optical signal after passing through the second optical fiber coupler. The first optical carrier signal is introduced into a long delay τ through a single-mode optical fiber, and then coupled with the first local-oscillation optical signal through a third optical fiber coupler to obtain a first coupled signal, which enters the first processing module. The second optical carrier signal is coupled with the second local-oscillation optical signal through a fourth optical fiber coupler to obtain a second coupled signal, which enters the second processing module. In the first processing module, a first photodetector, a first filter and a first amplifier are sequentially arranged to perform photoelectric conversion, filter only the beat signal of the positive first-order sideband of the optical carrier and the local-oscillation optical signal, and amplify the electrical signal filtered by the filter. In the second processing module, an adjustable optical fiber delay line, a second photodetector, a second filter and a second amplifier are sequentially arranged to introduce a phase shift into the second coupled signal perform photoelectric conversion, filter only the beat signal of the positive first-order sideband of the optical carrier and the local-oscillation optical signal, and amplify the electrical signal filtered by the filter. By adjusting the adjustable optical fiber delay line, the relative phase difference between the electrical signals output by the first optical processing module and the second optical processing module is K is an integer; the first light processing module and the second light processing module output the electrical signal received by the double balanced mixer, and the two signals are mixed; the low-pass filter receives the electrical signal output by the double balanced mixer, and filters out the high-frequency components; the phase noise of the measured microwave signal is obtained by analyzing and calculating the electrical signal output by the low-pass filter through the signal analyzer.

[0064] The broadband microwave photon phase noise measuring device provided by the application does not need to use an optical filter, avoids the limitation of the roll-off slope of the optical filter on the low-frequency signal measurement capability, and expands the working bandwidth of the system.

[0065] The broadband microwave photon phase noise measuring device provided by the application uses heterodyne detection technology, only needs to use low-frequency photoelectric detectors, electrical filters, electrical amplifiers and electrical mixers and other electronic devices, avoids the limitation of electronic devices on the high-frequency signal measurement capability, and makes the phase noise measurement system of the application have the advantages of low cost and large bandwidth.

[0066] The broadband microwave photon phase noise measuring device provided by the application does not need to use a high-performance, low-phase-noise reference signal source, avoids the limitation of the reference source on the measured signal, expands the working bandwidth of the phase noise measurement system, and reduces the system cost.

[0067] The broadband microwave photon phase noise measuring device matches the delay of the first branch and the second branch, suppresses the noise of the local oscillator light source, makes the phase noise measurement system of the application have the characteristics of high measurement sensitivity and low noise floor.

[0068] As a further improvement of the application, the electro-optic intensity modulator is preferably a broadband electro-optic intensity modulator, which is beneficial to expand the measurement bandwidth of the system; the electro-optic intensity modulator can be a Mach-Zehnder modulator; the tunable laser is preferably a narrow-linewidth high-tuning-precision laser, which can reduce the noise floor of the system and improve the measurement sensitivity; the first photoelectric detector and the second photoelectric detector are preferably photoelectric detectors with high photoelectric conversion efficiency, the first amplifier and the second amplifier are preferably low-noise amplifiers, and the signal analysis instrument is preferably a fast Fourier transform analyzer.

[0069] The application further provides a broadband microwave photon phase noise measurement method applied to the broadband microwave photon phase noise measurement device described above, and includes the following steps:

[0070] S1: generating a continuous optical carrier signal and a frequency-tunable local oscillator light signal, and modulating the continuous optical carrier signal by using a measured microwave signal of a measured microwave source;

[0071] S2: divide the modulated continuous optical carrier signal into a first optical carrier signal and a second optical carrier signal; use the second optical fiber coupler to divide the local light signal into a first local light signal and a second local light signal, wherein the first local light signal enters the first branch and the second local light signal enters the second branch; and introduce a long delay in the first optical carrier signal to obtain a delayed optical carrier signal;

[0072] S3: couple the delayed optical carrier signal and the first local light signal to obtain a first coupled signal; and couple the second optical carrier signal and the second local light signal to obtain a second coupled signal;

[0073] S4: first adjust the delay difference between the first branch and the second branch to be within 1 ns, and then finely adjust the delay difference so that the output signals of the first processing module and the second processing module are in quadrature, and then perform heterodyne detection, filtering and amplification on the delayed first coupled signal and the second coupled signal, respectively;

[0074] S5: mix the processed first coupled signal and the second coupled signal and filter out high frequency components therefrom to obtain a to-be-detected signal;

[0075] S6: analyze and calculate the to-be-detected signal to obtain the phase noise of the to-be-measured microwave signal.

[0076] The wideband microwave photonic phase noise measurement method in the embodiment is based on the aforementioned wideband microwave photonic phase noise measurement device, and thus the specific implementation of the method can be seen from the foregoing embodiment part of the wideband microwave photonic phase noise measurement device, and thus the specific implementation can be referred to the description of the corresponding embodiment part, which will not be introduced here.

[0077] In order to facilitate understanding of the technical scheme of the present application, the following will be combined with Figure 1 Briefly describe the measurement principle of the measurement system: the optical signal output by the laser is represented as:

[0078] E in (t)=E0exp(jω c t)

[0079] Wherein, E0 is the electric field amplitude of the optical signal, ω c is the angular frequency of the optical signal, and the signal input into the Mach-Zehnder modulator can be represented as:

[0080]

[0081] Wherein, V is the amplitude of the input radio frequency signal, ω is the angular frequency of the to-be-measured microwave signal, The phase noise of the microwave signal to be measured; the output signal of the Mach-Zehnder modulator working in push-pull mode can be represented as:

[0082]

[0083] Wherein, V π is the half-wave voltage of the Mach-Zehnder modulator; under small signal modulation, according to the first Bessel function series expansion:

[0084]

[0085] Wherein, m1 is the modulation coefficient of the Mach-Zehnder modulator; the output signal of the Mach-Zehnder modulator is divided into two paths through the first optical fiber coupler, wherein the upper branch signal is introduced into a long delay through a single-mode optical fiber, and can be represented as:

[0086]

[0087] Wherein, τ is the optical fiber delay; the lower branch signal can be represented as:

[0088]

[0089] Using a tunable laser, by adjusting its frequency, it is closer to the positive first-order sideband, and through the second optical fiber coupler, it is divided into two paths, which are coupled into the first branch and the second branch through the third optical fiber coupler and the fourth optical fiber coupler respectively, assuming its frequency is ω c +ω LO , the phase noise is The delay difference between the first branch and the second branch is Δτ, then the optical signal before the first photodetector in the first branch can be represented as:

[0090]

[0091] The second branch is introduced into the phase shift Then the optical signal before the second photodetector in the second branch can be represented as:

[0092]

[0093] The optical signals in the first branch and the second branch are input into the first photodetector and the second photodetector respectively for heterodyne detection; and by selecting the center frequency and bandwidth of the first filter and the second filter, only the positive first-order sideband of the optical carrier and the beat signal of the local oscillator signal are filtered out, then the output signal of the first amplifier can be represented as:

[0094]

[0095] The output signal of the second amplifier can be represented as:

[0096]

[0097] The electric signal outputted from the first branch and the second branch is received by the double balanced mixer, and mixed, and the mixed electric signal is inputted into the low pass filter to filter the high frequency component, and the output signal of the low pass filter can be expressed as:

[0098]

[0099] By adjusting to make be an integer; the delay of the first branch and the second branch is adjusted to make Δτ=0 to suppress the noise of the local light source; and the output signal of the low pass filter can be expressed as:

[0100]

[0101] wherein K is the calibration coefficient; and it is obvious that the phase noise information of the measured microwave source is contained in the above formula, and the power spectrum of the output signal can be expressed as:

[0102]

[0103] wherein S o (f) is the double sideband phase noise power spectrum density of the measured microwave signal, and according to the definition, the single sideband power spectrum density (phase noise) can be written as:

[0104]

[0105] After the signal power spectrum is collected by the signal analyzer, the phase noise of the measured microwave source can be calculated by the above formula.

[0106] Obviously, the above embodiments are only examples for clearly illustrating, and are not the limitation of the embodiments. For the ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description. All the embodiments are not required to be exhausted, and the obvious changes or variations derived from the above are still within the protection scope of the present application.

Claims

1. A broadband microwave photonic phase noise measurement apparatus, characterized by: The application relates to a microwave phase noise measurement system. The system comprises: a light beam generation module for generating a continuous light carrier signal modulated by a microwave signal to be measured of a microwave source to be measured and a frequency-adjustable local light signal; a coupling module for dividing the local light signal into two signals entering a first branch and a second branch respectively, and dividing the modulated light carrier signal into two signals, one of which is coupled into the first branch to obtain a first coupled signal, and the other of which is coupled into the second branch after being introduced into a long delay to obtain a second coupled signal; a first processing module arranged in the first branch, for introducing a delay into the first coupled signal to match the delay of the first branch and the second branch, so that the delay difference between the first coupled signal and the second coupled signal is controlled within 1 ns, to suppress the noise of the local light signal, and the first coupled signal after the delay is subjected to heterodyne detection, filtering and amplification in sequence; a second processing module arranged in the second branch, for introducing a phase shift into the second coupled signal to finely adjust the delay difference, so that the delay difference changes within 100 ps, so that the output signals of the first processing module and the second processing module are in quadrature, and the second coupled signal after the delay is subjected to heterodyne detection, filtering and amplification in sequence; an analysis module for mixing the output signals of the first processing module and the second processing module and filtering out high-frequency components in the output signals; the filtered signals are analyzed and calculated to obtain the phase noise of the microwave signal to be measured; 2. The wideband microwave photonic phase noise measurement apparatus of claim 1, wherein: wherein the frequency of the local light signal is close to the frequency of the continuous light carrier signal, and the high-frequency microwave signal to be measured can be down-converted into a low-frequency signal after the heterodyne detection of the first processing module and the second processing module, and the frequency of the low-frequency signal is within the working frequency range of conventional electrical components. The light beam generation module comprises: a laser for generating a continuous light carrier signal; an electro-optical intensity modulator for modulating the light carrier signal generated by the laser by using the microwave signal to be measured of the microwave source to be measured; 3. The wideband microwave photonic phase noise measurement apparatus of claim 1, wherein: a tunable laser for generating a frequency-adjustable local light signal. The coupling module comprises: a first optical fiber coupler for dividing the modulated light carrier signal into a first light carrier signal and a second light carrier signal; a single-mode optical fiber for introducing a long delay into the first light carrier signal to obtain a delayed light carrier signal; a second optical fiber coupler for dividing the local light signal into a first local light signal and a second local light signal, wherein the first local light signal enters the first branch, and the second local light signal enters the second branch; a third optical fiber coupler for coupling the delayed light carrier signal and the first local light signal to obtain a first coupled signal; 4. The wideband microwave photonic phase noise measurement apparatus of claim 3, wherein: a fourth optical fiber coupler for coupling the second light carrier signal and the second local light signal to obtain a second coupled signal. The first processing module comprises, in sequence, A first tunable optical fiber delay line is used to adjust the delay of the first coupled signal, and the delay difference between the signal transmitted in the first branch and the signal transmitted in the second branch is within 1 ns, so as to offset the phase noise of the local light; A first photodetector is used to receive the first coupled signal and perform heterodyne detection; A first filter is used to filter out only the positive first-order sideband of the first optical carrier signal and the beat signal of the first local light signal; A first amplifier is used to amplify the electrical signal output by the first filter.

5. The wideband microwave photonic phase noise measurement apparatus of claim 3, wherein: The second processing module comprises, in sequence: a second tunable optical fiber delay line for fine tuning the delay difference in the range of 100 ps by introducing a phase shift into the second coupled signal such that the relative phase difference between the electrical signals output by the first processing module and the second processing module is k is an integer; A second photodetector is used to receive the second coupled signal with a phase shift and perform heterodyne detection; A second filter is used to filter out only the positive first-order sideband of the second optical carrier signal and the beat signal of the second local light signal; A second amplifier is used to receive and amplify the electrical signal output by the second filter.

6. The wideband microwave photonic phase noise measurement apparatus of claim 1, wherein: The analysis module comprises: A double-balanced mixer is used to receive the electrical signals output by the first processing module and the second processing module and perform mixing; A low-pass filter is used to receive the electrical signal output by the double-balanced mixer and filter out high-frequency components therein; A signal analyzer is used to analyze and calculate the electrical signal output by the low-pass filter to obtain the phase noise of the microwave signal to be measured.

7. The wideband microwave photonic phase noise measurement apparatus of claim 2, wherein: The electro-optic intensity modulator is a broadband Mach-Zehnder modulator.

8. The wideband microwave photonic phase noise measurement apparatus of claim 2, wherein: The tunable laser is a narrow-line-width high-tuning-precision laser.

9. A broadband microwave photonic phase noise measurement method, characterized in that: The application is applied to a broadband microwave photonic phase noise measurement device as claimed in any one of claims 1-8, and comprises the following steps: S1: generating a continuous optical carrier signal and a frequency-tunable local light signal, and modulating the continuous optical carrier signal by using a microwave signal to be measured of a microwave source to be measured; S2: dividing the modulated continuous optical carrier signal into a first optical carrier signal and a second optical carrier signal; using a second optical fiber coupler to divide the local light signal into a first local light signal and a second local light signal, wherein the first local light signal enters a first branch, and the second local light signal enters a second branch; and introducing a long delay into the first optical carrier signal to obtain a delayed optical carrier signal; S3: coupling the delayed optical carrier signal and the first local light signal to obtain a first coupled signal; and coupling the second optical carrier signal and the second local light signal to obtain a second coupled signal; S4: first, adjusting the delay difference between the first branch and the second branch to be within 1 ns, and then finely adjusting the delay difference, so that the output signals of the first processing module and the second processing module are in phase quadrature, and the delayed first coupled signal and the second coupled signal are sequentially subjected to heterodyne detection, filtering and amplification; S5: mixing the processed first coupled signal and the second coupled signal and filtering out high-frequency components therein to obtain a signal to be detected. S6: analyzing and calculating the to-be-detected signal to obtain the phase noise of the to-be-detected microwave signal.

10. The wideband microwave photonic phase noise measurement method of claim 9, wherein: The filtering in step S4 is specifically filtering out the beat frequency signal of the positive first-order sideband of the optical carrier and the local oscillation optical signal.

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